Rear Caliper

[ahebron]

2000 BMW R1150GS
Rear caliper kept locking on in the morning when first ridden when the bike was kept outside on our recent ride round the top of the South Island. Removed the caliper and saw the front piston would move and retract but the rear wouldnt retract so ordered replacement pistons and seals from Motorworks.
Fitted the parts today using the supplied lube. I noticed that the spring which sits on the top of the pads was bent on the one edge so I straightened it, hope this is right and fitted it with the arrow to the front of the bike. Bled the system using my vac pump which was easy to do.
What I am noticing when I press the pedal is that the front piston is moving first which makes the front of the caliper twist on its mounts as the rear piston lags behind. As Steptoe says giving the caliper a shove on the logo evens frees up the caliper and this also evens it up on the pins but this would be a bit boring to do everytime I use the rear brake.
With the caliper removed and pads out the front piston moves first and rear piston follows but not to the same amount.
Is this normal movement for the caliper?

Thanks
Adrian

 

[DrFarkoff]

Yes basically its just a little freer than the other one and it moves first

but as soon as you stop it the pressure applies to the second piston and brings it out

The when they are both out in a working position as soon as you apply the brakes the pressure is uniform against the two pistons, because they are pushing the brake pad against the disc and that should align the calliper more squarely

 

[Riceburner]

Make sure you lube the slide pins regularly as well.

 

[DrFarkoff]

Make sure you lube the slide pins regularly as well.

BUT NOT WITH COPPASLIP or any other mineral based grease Use silicone or Rubber grease

as I have found on many an occasion and the requiring the rubber boots as they had swollen up !

 

[buellzebub]

BUT NOT WITH COPPASLIP

+1 It's an anti-seize compound, not a lubricant.

 

[dubster]

Yes basically its just a little freer than the other one and it moves first

but as soon as you stop it the pressure applies to the second piston and brings it out

The when they are both out in a working position as soon as you apply the brakes the pressure is uniform against the two pistons, because they are pushing the brake pad against the disc and that should align the calliper more squarely

Thanks, same behaviour with my rear caliper - I always wondered about that but it all makes sense now.

 

[Riceburner]

The ONLY thing i use copaslip on is threads.